In the present day various apparatus are available to measure thickness of crystalline layers that may be free standing or disposed on a substrate. Although many techniques are available to measure a crystalline layer in a static fashion, such as when the layer is disposed on a substrate at room temperature, measurement of layer thickness during formation of a crystalline layer may be more challenging. This is especially so when growth takes place under elevated temperature or under special ambient.
In the present day techniques have been developed to grow single crystalline (monocrystalline) sheets from a melt of a given material such as silicon or sapphire. This may be accomplished by crystallizing a thin solid layer of the given material on the surface of a melt and drawing an edge of the layer along the melt or pulling the layer from the melt according to known techniques. Control of the crystallinity and thickness of such monocrystalline sheets may depend upon a number of factors, including growth temperature, pulling rate, and so forth. Accordingly, precise control of growth parameters may be desirable. Moreover, it may be desirable to measure properties of the monocrystalline sheet during growth of the monocrystalline sheet in order to obtain “real time” information to determine if properties of the monocrystalline sheet are as desired.
However, there is a lack of techniques for measurement of properties of monocrystalline sheets during growth. Measurement is complicated by the fact that a crystalline sheet may be growing on or within a melt at an elevated temperature, which provides challenges to delivering a probe signal to the crystalline sheet and detecting a measurement signal with enough accuracy to properly monitor the growing sheet. It is with respect to these and other considerations that the present improvements have been needed.